One of my users is having an issue when she opens Outlook where she gets an
error that says the CRM client can't load because cookies have been disabled
within her browser settings. And then she gets the infamous error: "An
error occurred loading Microsoft CRM functionality..."

This was working fine yesterday -- she comes in this morning and now it's
not working. I checked her browser settings and cookies aren't disabled.
Just in case I went in and added the CRM server to her list of trusted sites
within her Intranet zone and that didn't make a difference. No changes have
been made. This is on a terminal server -- Outlook 2003, all current service
packs and running CRM 3.0 V3C.

Any ideas?

I ran into this once where cookies were enabled, but was getting the
same error message. I disabled cookies in internet options applied
the change and then reenabled cookies and applied and it went away for
good...

You could also try resetting security zones etc. back to default.